1. Field of the Invention
The present invention is directed to using wires as curves that effect object or model deformation and, more particularly, to a system where wires, independent of the characteristics of the object, can be used to give definition to an object and shape its deformable features.
2. Description of the Related Art
The modeling and animation of deformable objects is an active area of research. Free-form deformations (FFDs) and its variants are popular and provide a high level of geometric control over the deformation. These approaches typically involve the definition and deformation of a lattice structure of control points. By deforming the space defined by the lattice any object within the space is also deformed. An object embedded within the lattice is deformed by defining a mapping from the object to the undeformed lattice. The point in space in the deformed lattice is the deformation imparted to the point. The user deals with a level of detail dictated by the density of the control lattice. While very useful for coarse-scale deformations of an object, this technique can be difficult to use for finer-scale deformations, since a very dense control lattice and customized control lattice shape may be required. To perform fine control the "resolution" of the lattice needs to approach that of the portion of an object that is to be deformed. Manipulating a dense control lattice is often harder than deforming the underlying geometry directly, and arbitrarily shaped lattices (other than a box shape) can be cumbersome to construct.
What is needed is a deformation mechanism that is easy to control.
Axial deformations provide a more compact representation in which a one-dimensional primitive such as a line segment or curve is used to define an implicit global deformation. Axial deformations also use the notion of a reference curve and a closest point computation. The axial deformation technique relates two Frenet frames attached at the closest point on the curve and the corresponding point on the reference curve. The deformation imparted to a point is a portion of a transformation from the reference curve's Frenet frame to the Frenet frame on the deformed curve. The proportion is based on an interpolation of the closest distance of the point to the reference curve between two cutoff radii. However, axial deformations cannot provide a coarse-scale representation of the object surface, or provide an easily manipulated deformation primitive that highlight and track the salient deformable features of the object. In axial deformations as well as lattice based deformations the underlying geometric model of the object needs to be apparent to the user separate and apart from the line segment or curve used to define the axial deformation primitive.
What is needed is a primitive that provides a coarse-scale representation of the object surface and a primitive that can be directly manipulated while highlighting and tracking the deformable features of the object and in which the underlying geometric model of the object need not be apparent to the user.